Nonmalignant respiratory disease among hematite mine workers in China.
The mortality risk of nonmalignant respiratory disease among hematite workers in the Longyan and Taochong mines of China was investigated in a retrospective cohort study covering the period 1970-1982. The cohort was limited to men and consisted of 5406 underground miners, of whom 1335 (25%) were diagnosed as having silicosis. Among those with silicosis, 560 (42%) were diagnosed as having silicotuberculosis. Among the 490 underground miners who died, 278 (57%) died of nonmalignant respiratory disease. The relative risk for death due to nonmalignant respiratory disease for stage III silicotics compared to nonsilicotics was almost 100-fold. High dust exposure was associated with a statistically significant increase in risk of death due to nonmalignant respiratory disease (relative risk 5.3). The relative risk associated with jobs with high dust exposure before the introduction of industrial hygiene controls was 7.7, and the corresponding value for after their introduction was 2.3. There is a need for continued close monitoring of industrial hygiene in these mines.